电学调制二维材料表面摩擦能量耗散机制的研究

Potential Energy Surface (PES) is an important theoretical model to study atomic scale friction based on density functional theory, and an effective mean to predict tribological properties including nanoscale stick-slip process and frictional energy dissipation. However, current researches based on PES have lots of limitations such as unclear physical essence and influence factors, lack of modulation methods, failure to combine with experiments. To deal with the problems, a new route is proposed to study electrically modulated friction with PES. The electronic properties of two-dimensional materials (e.g. carriers’ density and mobility, electron cloud distribution, etc) will be controlled in situ by applying an external potential difference and/or bias voltage. Based on the combination of ultrahigh vacuum atomic force microscope and density functional theory, we will study the coupling mechanism of surface electronic structure, nanoscale stick-slip process and friction energy dissipation using PES as the research media. We will build theoretical model of friction energy dissipation affected by electronic structure and proved with experiment data. Furthermore, we will develop a new in situ control technology of friction energy dissipation by surface electronic structure, and explore the key method of regulating and reducing the interface friction through electrical modulation. Achievements of this research are helpful and vital in promoting the friction mechanism studies and extending their application fields.

表面接触势能量起伏是基于密度泛函理论计算，针对原子级摩擦提出的重要理论分析模型，可有效预测微观摩擦黏滑运动过程与摩擦能量耗散，分析摩擦特性变化规律。目前国内外接触势能量起伏的相关微观摩擦学研究面临物理本质及影响因素不清晰、调控方法有限、未能与实验研究相结合等共性问题。针对上述问题，项目组提出采用外加电势差、偏压等方式原位调制二维纳米材料表面载流子密度、载流子迁移率、电子云分布等电子学结构特性，结合超高真空原子力系统与密度泛函理论计算，以表面接触势能量起伏为中间载体，研究材料电子学性质与微观摩擦黏滑过程、摩擦能量耗散的耦合机制，建立材料电子学特性影响摩擦能量耗散的理论模型并进行实验验证。并在此基础上研究通过表面电子学结构特性原位调控摩擦能量耗散的新方法，探索基于电学手段调控界面摩擦特性、降低的关键技术。该研究的顺利实施对推动摩擦学机理研究，拓展其应用领域有重要的帮助和支撑作用。

本项目以摩擦能量耗散机理和超滑调控技术为主要研究方向，从科研仪器建设、实验测试和理论计算三方面开展研究工作。设计搭建了超高真空原子力显微镜系统，并改装接入外加电学调控系统和光路模块，为电场调控二维材料摩擦学特性提供了仪器支撑与平台。本项目以石墨烯、二硫化钼为代表的二维纳米材料为研究体系，采用电学调控的方式调制材料表面电子学结构，通过密度泛函理论计算和超高真空原子力显微镜进行摩擦能量耗散的实验对照研究，挖掘表面电子学结构与摩擦能量耗散的关联机制。通过揭示材料电子学性质与超滑的关联机制，获得了基于材料电子学性质调控超滑性能的技术路径。